The present invention relates generally to a fibrous mat for hot molding to molded articles.
Multilayer fibrous mats, particularly those with special surface coatings are known. In particular, a multilayer fibrous mat for producing molded articles in a press mold by exposing the fibrous mat to pressure and elevated temperature and formed from cellulose, lignocellulose or similar fibers, whose two surface layers are also formed from a tangled fiber fleece and provided with at least a proportion of thermosetting synthetic resins, is known. A thermoplastic binder-containing central tangled fiber layer and two outer surface layers provided with thermosetting binders are produced by the layerwise placing of the mat material on a conveyor belt and in that state molded to molded articles, which simultaneously forms a firm union or sandwich of said multilayer arrangement. See, for example, German Patent No. P 32 33 385.
However, it has been found that the additional gluing of the surface layers with a thermosetting material which takes place in this process according to the partial flow principle during the production of the mat and during molding is at least partly absorbed by the absorbent central layer. This is disadvantageous in that in such known three-layer mats, the thermal and mechanical surface treatment is lost through the thermosetting binder used therein undersirably migrating into the central layer. This effect can only be compensated by the addition of larger quantities of thermosetting binder being applied to the surface layer fibers, which would make the desired end product much more expensive.
Another known process for producing insulating plates, using mineral fibers as a basis, can be realized when the non-woven fabric is applied to a moving surface fiber fleece during production, so that during compression the insulating plate is joined to the fleece carrier (DE.OS No. 28 53 316).
In product-dependent manner, particular attention has long been paid to the processing of wood fiber materials of the present type and, non-woven fabrics comprising natural or mineral fibers and the like to plates or three-dimensionally shaped products. The nature of the surface treatment for these products can range from the simplest resin enrichment, primers or varnishes to printing and lining with films or lamination with plastics and the like.
The application of surface layers to supporting central layers, either in the form of special surface laeer gluing treatments, additional lining material or the like, generally leads to the desired improved surface characteristics, but is generally also linked with a sealing of the surface in the sense of being impermeable to gases or liquids. This can be disadvantageous in many cases and particularly when the processing of such mats to molded articles excludes certain procedures or other technically simply performable process steps. Reference is made to this in connection with the production-favorable vacuum deep drawing process for coordinating such molded articles with thermoplastic films, as well as to certain characteristics of completely molded parts, which are considered to be more advantageous when used as linings in passenger areas of motor vehicles if they ensure a certain air permeability and moisture absorption, which further significantly improves the climatic conditions within such passenger areas.